The present invention generally pertains to descrambling systems for subscriber communication networks and is particularly directed to systems for enabling descrambling on a selective-subscription basis.
Selective-subscription subscriber communication networks provide for descrambling of signals on a prepaid basis and/or on an impulse-purchase basis.
In one type of prepaid descrambling system, a descrambler at the subscriber terminal is adapted to descramble all communications received over a given communications channel, such as, for example, all of the programs broadcast over a given television channel. When service is discontinued, the descrambler must be modified to prevent descrambling of signals received over the given channel. In another type of prepaid descrambling system, descrambling is enabled by an enable signal addressed to the descrambler at the subscriber terminal.
Typical impulse-purchase subscriber communication network descrambling systems are described in U.S. Pat. Nos. 4,484,217 to Block et al; 2,573,349 to Miller at al; 2,788,387 to Druz; 2,864,885 to Morris; 2,866,962 to Ellett; 3,531,586 to Bass et al; 3,736,369 to Vogelman et al; 3,916,091 to Kirk, Jr. et al; and 4,130,833 to Chomet.
Bass et al describes an impulse-purchase system for a subscriber television network in which a debit (cost) signal related to the viewing cost of a given television program is transmitted to each subscriber terminal and processed in relation to an indication of the subscriber's established credit to determine whether the subscriber is authorized to view the given program. In the Bass et al system subscriber credit is established in response to the insertion of coins into a coin mechanism included in the subscriber terminal. If after a subscriber has accepted a given program for viewing the program is cancelled, such as for technical reasons, a credit signal is transmitted to the subscriber terminals to restore the subscriber's established credit by an appropriate amount.
Druz describes an impulse-purchase system for a subscriber television network in which a cost signal containing charging information related to the cost of viewing a given program is transmitted to the subscribers and upon acceptance by a subscriber of the program for viewing, the charging information is recorded by a recording device at the subscriber terminal. The recorded charging information is collected or read from the recording device periodically and the subscriber subsequently is billed for the total cost of programs selected for viewing during the previous period.
Both of these prior art systems require some type of post-viewing collection from the subscriber. With the Bass et al system coins must be collected from each individual subscriber's coin mechanism; and with the Druz system the recorded charging information must be collected from each individual subscriber's recording device.
One object of the present invention is to provide an impulse-purchase descrambling system which enables other payment methods in addition, or alternative, to such post-viewing collection from each individual subscriber terminal.
Another object of the present invention is to provide an impulse-purchase descrambling system that will enable special event television programs transmitted on a given pay-TV channel to be selected for viewing on an impulse-purchase basis by subscribers who do not regularly subscribe to all of the programming on such channel.
Still another object of the present invention is to provide a descrambling system that can be controlled by received signals to either descramble scrambled signals on a prepaid basis or to offer descrambling on an impulse-subscriber basis depending upon the subscription status of the subscriber and whether the signal is authorized for descrambling on an impulse-purchase basis.
A further object of the present invention is to provide a system for preventing a subscriber from being able to enable descrambling in a selective-subscription subscriber communication network through such deceit as substituting other signals for transmitted signals, such as a cost signal, that are received and processed at the subscriber terminal to enable descrambling.